Effect of multiparity on morphometry and oestrogen receptor expression of pelvic and perineal striated muscles in rabbits: is serum oestradiol relevant?

• Published in: European journal of obstetrics & gynecology and reproductive biology Vol. 169; no. 1; pp. 113 - 120
• Main Authors: López-García, K, E.Cuevas, Corona-Quintanilla, D.L, Jiménez-Estrada, I, Martínez-Gómez, M, Castelán, F
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.07.2013
• Subjects: Animals; Estradiol - blood; Estrogen Receptor alpha - biosynthesis; Estrogen Receptor beta - biosynthesis; Female; Multiparity; Muscle Fibers, Skeletal - ultrastructure; Muscle, Skeletal - physiology; Muscle, Skeletal - ultrastructure; Obstetrics and Gynecology; Oestradiol; Oestrogen receptors; Parity - physiology; Pelvic floor; Perineum; Pregnancy; Pregnancy, Animal - physiology; Rabbits; Striated muscles; Pelvic floor; Striated muscles; Oestradiol; Perineum; Multiparity; Oestrogen receptors
• ISSN: 0301-2115; 1872-7654
• DOI: 10.1016/j.ejogrb.2013.03.032

Abstract Objective To determine changes in morphometry and expression of oestrogen receptors (OR) in the pubococcygeus and bulbospongiosus muscles, and the concentration of serum oestradiol associated with multiparity. Study design Twelve chinchilla-breed female rabbits were divided into multiparas who had undergone four consecutive deliveries and age-matched virgin nulliparas. Pubococcygeus and bulbospongiosus muscles were surgically removed from each rabbit and processed histologically. Fibre cross-sectional area, number of peripheral nuclei, and expression of ORα and ORβ were measured for each muscle. Serum samples were obtained and the concentration of serum oestradiol was quantified. Results Multiparity increased ( p ≤ 0.05) fibre cross-sectional area and the number of peripheral nuclei per fibre in pubococcygeus muscle, but not in bulbospongiosus muscle. Expression of both ORα and ORβ was high ( p ≤ 0.05) in both muscles from multiparous rabbits. A rise in serum oestradiol was measured at the end of the second pregnancy, which was absent ( p ≤ 0.05) at the end of the fourth pregnancy. The concentration of serum oestradiol was similar ( p > 0.05) in nulliparous and multiparous rabbits. Conclusions Multiparity caused morphometric changes in pubococcygeus muscle but not in bulbospongiosus muscle. As OR expression was high for both muscles, some properties related to fibre composition or muscle physiology could be affected. The finding that serum oestradiol was not elevated at the end of the fourth pregnancy could be related to changes in pelvic and perineal muscles associated with multiparity.